oj.uz

Submission #817177

# Submission time Handle Problem Language Result Execution time Memory
817177 2023-08-09T10:06:52 Z t6twotwo Parking (CEOI22_parking) C++17
50 / 100
 91 ms 15508 KB 
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define FFOR(i,a,b,c) for(int i=(a);(c)>0?i<=(b):i>=(b);i+=(c))
#define FOOR(i,a,b) FFOR(i,a,(b)-1,1)
#define ROOF(i,a,b) FFOR(i,(b)-1,a,-1)
#define FOR(i,n) FOOR(i,0,n)
#define ROF(i,n) ROOF(i,0,n)
#define FORR(x,v) for(auto &x:v)
#define vc vector
#define sz(v) (int)((v).size())
#define bg begin()
#define en end()
#define em empty()
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define ppb pop_back()
#define eb emplace_back
#define bk back()
#define fr front()
#define pp pop()
#define all(v) (v).begin(),(v).end()
#define lla(v) (v).rbegin(),(v).rend()
#define f first
#define s second
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N,M;
    cin>>N>>M;
    vc<int> bot(M),top(M),x(N,-1),y(N),free;
    FOR(i,M){
        cin>>bot[i]>>top[i];
        bot[i]--,top[i]--;
        if(bot[i]!=-1) (x[bot[i]]==-1?x[bot[i]]:y[bot[i]])=i*2;
        if(top[i]!=-1) (x[top[i]]==-1?x[top[i]]:y[top[i]])=i*2+1;
        if(bot[i]==-1&&top[i]==-1) free.pb(i);
    }
    vc<pair<int,int>> ans;
    auto move=[&](int u,int v) {
        ans.eb(u,v);
        int a;
        if(top[u]!=-1){
            a=top[u];
            top[u]=-1;
        }else{
            a=bot[u];
            bot[u]=-1;
        }
        if(bot[v]==-1){
            (x[a]/2==u?x[a]:y[a])=v*2;
            bot[v]=a;
        }else{
            (x[a]/2==u?x[a]:y[a])=v*2+1;
            top[v]=a;
        }
        if(bot[u]==-1){
            free.pb(u);
        }
    };
    auto park=[&](int i,bool f){
        int a=x[i]/2;
        int b=y[i]/2;
        if(f) assert(top[a]==-1||top[b]==-1);
        if(top[b]!=-1) swap(a,b);
        move(a,b);
    };
    auto check=[&](){
        if(free.em){
            cout<<-1;
            exit(0);
        }
    };
    if(2*N<=M){
        auto good=[&](int a) {
            return (x[a]%2==1||top[x[a]/2]==-1)&&(y[a]%2==1||top[y[a]/2]==-1);
        };
        vc<bool> parked(N);
        FOR(i,N){
            if(x[i]%2==1&&y[i]%2==1){
                move(x[i]/2,free.bk);
                move(y[i]/2,free.bk);
                free.ppb;
            }
            if(x[i]/2==y[i]/2) parked[i]=1;
        }
        queue<int> q;
        FOR(i,N){
            if(!parked[i]&&good(i)){
                parked[i]=1;
                q.push(i);
            }
        }
        while(!q.em){
            int i=q.fr;q.pp;
            int a=x[i]/2;
            int b=y[i]/2;
            if(top[b]!=-1) swap(a,b);
            move(a,b);
            if(bot[a]!=-1){
                if(!parked[bot[a]]&&good(bot[a])){
                    parked[bot[a]]=1;
                    q.push(bot[a]);
                }
            }
        }
        FOR(i,N){
            if(!parked[i]){
                cout<<-1;
                return 0;
            }
        }
        cout<<sz(ans)<<"\n";
        for(auto[x,y]:ans){
            cout<<x+1<<" "<<y+1<<"\n";
        }
        return 0;
    }
    vc<bool> vis(M);
    vc<vc<int>> S;
    vc<vc<vc<int>>> T;
    FOR(i,M){
        if(vis[i]||bot[i]==top[i])continue;
        int j=i,k=bot[i],f=0;
        S.pb({k});
        T.pb({});
        while(1){
            T.bk.pb({});
            vis[j]=1;
            k=f?bot[j]:top[j];
            while(k!=bot[i]&&x[k]%2!=y[k]%2){
                T.bk.bk.pb(k);
                j^=(x[k]/2)^(y[k]/2);
                vis[j]=1;
                k=f?bot[j]:top[j];
            }
            if (k==bot[i])break;
            S.bk.pb(k);
            j^=(x[k]/2)^(y[k]/2);
            f^=1;
        }
    }
    FOR(i,sz(S)){
        if (sz(S[i])==1){
            check(); int t=free.bk; free.ppb;
            int a=x[S[i][0]];
            int b=y[S[i][0]];
            if (a%2==0) swap(a,b);
            move(a/2,t);
            ROF(j,sz(T[i][0])) park(T[i][0][j],0);
            move(b/2,t);
            continue;
        }
        check(); int t=free.bk; free.ppb;
        move(x[S[i][1]]/2,t);
        move(y[S[i][1]]/2,t);
        ROF(j,sz(T[i][0])) park(T[i][0][j],0);
        FOR(j,sz(T[i][1])) park(T[i][1][j],0);
        FFOR(j,3,sz(S[i])-1,2){
            check(); int t=free.bk;free.ppb;
            move(x[S[i][j]]/2,t);
            move(y[S[i][j]]/2,t);
            ROF(k,sz(T[i][j-1])) park(T[i][j-1][k],0);
            FOR(k,sz(T[i][j])) park(T[i][j][k],0);
            park(S[i][j-1],0);
        }
        park(S[i][0],0);
        if(sz(S[i])%2){
            ROF(j,sz(T[i].bk)) park(T[i].bk[j],1);
            park(S[i].bk,0);
        }
    }
    cout<<sz(ans)<<"\n";
    for(auto[x,y]:ans){
        cout<<x+1<<" "<<y+1<<"\n";
    }
    return 6/22;
}

Subtask #1
0.0 / 10.0

# Verdict Execution time Memory Grader output
1 Incorrect 0 ms 212 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 44 ms 5592 KB Output is correct
2 Correct 42 ms 5408 KB Output is correct
3 Correct 36 ms 4400 KB Output is correct
4 Correct 29 ms 4136 KB Output is correct
5 Correct 42 ms 5440 KB Output is correct

Subtask #3
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 340 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 340 KB Output is correct
4 Correct 1 ms 340 KB Output is correct
5 Correct 0 ms 340 KB Output is correct
6 Correct 1 ms 340 KB Output is correct
7 Correct 1 ms 340 KB Output is correct
8 Correct 0 ms 340 KB Output is correct
9 Correct 1 ms 340 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 340 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 340 KB Output is correct
4 Correct 1 ms 340 KB Output is correct
5 Correct 0 ms 340 KB Output is correct
6 Correct 1 ms 340 KB Output is correct
7 Correct 1 ms 340 KB Output is correct
8 Correct 0 ms 340 KB Output is correct
9 Correct 1 ms 340 KB Output is correct
10 Correct 91 ms 15508 KB Output is correct
11 Correct 33 ms 3424 KB Output is correct
12 Correct 36 ms 4736 KB Output is correct
13 Correct 70 ms 8892 KB Output is correct
14 Correct 50 ms 9152 KB Output is correct
15 Correct 49 ms 8916 KB Output is correct
16 Correct 85 ms 14412 KB Output is correct
17 Correct 43 ms 6628 KB Output is correct
18 Correct 79 ms 11720 KB Output is correct

Subtask #5
0.0 / 25.0

# Verdict Execution time Memory Grader output
1 Runtime error 2 ms 944 KB Execution killed with signal 6
2 Halted 0 ms 0 KB -

Subtask #6
0.0 / 15.0

# Verdict Execution time Memory Grader output
1 Incorrect 0 ms 212 KB Output isn't correct
2 Halted 0 ms 0 KB -